Is there anyone here that has known an adult with dandy-walker syndrome?

Many. Dandy walker malformation can be quite benign. It consists of a cyst of the cerebellum due to poor development of the foramina of the fourth ventricle. Some patients are mildly ataxic and the malformation is found only incidentally on a ct scan. Some are severe in infancy and need emergency surgery with shunt to relieve pressure. Once managed, most can lead healthy long lives.L.